Fault recorder is an automatic recording device which is used to monitor the operation of power system all the year round. It can record the system current, voltage and their derived quantities caused by short circuit fault, system oscillation, frequency collapse, voltage collapse and other large disturbances, such as active power, reactive power and system frequency. It is mainly the same as detecting the action behavior of relay protection and automatic safety device, understanding the variation law of various electrical quantities in the transient process, and checking the correctness of power system calculation program and model parameters. The fault recorder with excellent performance plays a very important role in ensuring the safe and reliable operation of power system.

All kinds of fault information of power system must be recorded by special fault recording or protection action report. Whether it is protection or special fault recorder, starting mainly uses the electrical quantity with obvious fault characteristics to start. The general starting quantity includes current and voltage sudden change starting, current and voltage out of limit starting, frequency change starting and switching value starting, etc. Generally, the collected information data is not filtered to keep the authenticity and real-time of fault information as much as possible. There are two types of information data, one is the alternating signal recording the instantaneous value of current and voltage, the other is the switching signal reflecting the positive and negative jump. The information data generally includes the part before the fault and the whole process of the fault. The instantaneous value waveform reflecting the change of current and voltage and the switching value reflecting the change of potential are drawn with the same time scale. The output part includes brief analysis report, important fault information data and the whole process of fault waveform.

Most of the fault recorders adopt the distributed system structure, so there are many devices connected, 96 analog signals and 128 switching signals. In this way, most of the signals in the substation can be monitored by the recorders at the same time, which greatly improves the amount of information for fault analysis and processing, and provides more and more comprehensive fault information for analysis problems. At the same time, it also avoids the problems of too many fault recording screens in the past substation, which lead to large occupation area, increased workload and asynchronous use, so that the data becomes more reliable and the calculation is more accurate.